1. Field of the Invention
The invention relates to the field of cutting implements. More particularly, the invention is a collapsible saw specially adapted to lock and to stabilize the blade into an operative configuration. The saw collapses into a compact unit for easy handling, transport, and storage.
2. Description of Related Art
There are a number of different types of collapsible saws commonly available. These saws are often used by campers, hunters or others who require a cutting tool that can be folded into a compact form to facilitate its handling, transport, and storage. U.S. Pat. No. 4,580,344 issued to Jinghage et al., U.S. Pat. No. 5,067,190 issued to Gagnon, and German Patent No. 132,794 issued to Schippert each describe a collapsible saw. The prior art consists primarily of two types of collapsible saws. The first type involves assembling multiple members interconnected by fittings, bolts, and pivot pins as in Gagnon and Schippert, where tightened bolts secure the assembly together. The second type involves assembling multiple members interconnected by pivot pins as in Jinghage et al., where the tension between the interconnections themselves secures the assembly together without any bolts.
For saws of the first type, changing the saw from a collapsed configuration to an operative configuration requires first disassembling the saw from its collapsed configuration. The disassembly may involve removing the collapsed saw from a carrying case, unscrewing bolts, or both. A requirement to unscrew bolts in disassembly of a saw from its collapsed configuration can be a tedious step precedent to placing the saw in its operative configuration. The bolts may adequately secure a saw in the collapsed configuration, but present an obstacle to disassembly. A user may have to carry tools along with the saw, presenting an additional obstacle. A carrying case may also adequately secure the parts of a saw in a collapsed configuration, but adds to the bulk of the collapsed saw. Furthermore, often a carrying case is needed to protect users from being cut by an exposed blade during handling, transport, or storage. Also, the collapsed saw may consist of multiple, separated parts that must be placed in a carrying case to avoid misplacement or loss of a part. Once removed from their carrying case, some collapsed saws include a frame held together with pivot pins and are essentially "unfolded" into a position where a blade can then be attached. Other collapsed saws include multiple parts that are joined by interlocking fittings rather than pivot pins. Still other saws include both pivot pins and interlocking fittings.
All collapsible saws of the first type use one or more bolts which must be tightened, usually in association with attaching the blade to the frame, to secure the assembly together. Once the blade is attached, it must be secured in place either by directly bolting the blade to the frame or by bolting the frame into a position that applies tension to the blade. Applying tension to the blade is needed both to hold the assembly together in the operative configuration and to prevent the blade from bending or twisting during use. Bending or twisting of the blade may create several problems such as increased difficulty in cutting, increased likelihood of blade breakage, and increased likelihood of injury to the user as a result of the difficult cutting or blade breakage. If cutting is difficult because of a bending or twisting blade, then a user will have to apply more force to the cutting motions and any sudden slip of the user's grip or of the saw blade is more likely to injure the user or damage the saw. Similarly, if a blade suddenly breaks because of a bending or twisting blade, then the user could be injured or the saw could be damaged, especially if the user is applying more force because of difficulty in cutting. Accordingly, it is important in collapsible saws to maintain sufficient blade tension such that the user is not injured and the saw is not damaged.
However, a blade that is over tightened also creates problems. Essentially, over tightening a blade will place some member of the saw into a state of critical stress such that the member deforms, cracks, breaks, or is otherwise damaged. The affected member may be a joint, a fitting, or even the blade. Whatever the damage and the particular member affected, additional force placed on the saw during use can result in sudden and undesired collapse of the saw and potential injury to the user. Over tightening is a particular problem among saws which require a wrench, screwdriver, or other tool to tighten bolts, since it is easy for a user to overestimate the tension required. Manufacturers may attempt to overcome the hazards of over tightening by constructing a frame capable of withstanding high stresses, however, it is usually desirable for a collapsible saw to be lightweight in addition to being compact. High stress construction often yields a saw heavier in weight.
The second type of collapsible saw, with members interconnected by pivot pins only and tension between interconnections securing the assembly, overcomes the problems discussed above, but may possess other problems. The second type of saw generally requires less time and effort to disassemble the saw from a collapsed configuration and reassemble it into an operative configuration. Because the saw uses only pivot pins, no tools are necessary and blade tension is generally predetermined by the manufacturer. Once the blade is locked into a predetermined position, dictating a predetermined tension, the saw is ready to use. Such a saw may also include an internal compartment for storing the blade while the saw is collapsed to prevent the need for a carrying case. Since the saw is entirely connected with pivot pins, there is likewise no need for a carrying case to prevent the loss of multiple, separated parts.
Unfortunately, the mechanical solutions to the problems of the first type of saw created new problems in the second type of saw. In prior art collapsible saws, connection of all the saw members with pivot pins eliminated loss of separated parts and tensioning problems, but forced the saw to be less compact. When the saw is in a collapsed configuration, the members are folded against one another rather than nested within one another so the collapsed saw is more bulky. Such a folded, rather than nested, configuration is mandated by the prior art interconnection with pivot pins. According to the prior art, nesting could take place if a pin was replaced with a bolt, but then an extra assembly step and a separated part would be present.
Thus, it can be seen from the above discussion that it would be an improvement in the art to provide a collapsible saw of the second type which resolved the problems of the first type of saw as well as the problems created by prior art saws of the second type. Specifically, this means providing a collapsible saw that connects the saw members with pivot pins, but still collapses into a nested arrangement. It would also be an improvement for a collapsible saw to include multiple blades in the nested arrangement.